Marine keel cooler

ABSTRACT

A marine keel cooler is disclosed which includes two header assemblies each adapted to be mounted on the exterior of a vessel&#39;&#39;s hull. Each header assembly includes a stud plate and at least two separable members formed of an elastomeric material. The members are formed with semicylindrical recesses which cooperate with adjacent recesses to form openings which receive and grip the ends of the heat exchanger tubes. Relatively soft heat resistant seals are positioned over the ends of the tubes within the openings and are tightly gripped when the parts of the header assembly are bolted together. When fluted tubes are used, the parts are proportioned so that the tube is radially contracted to a uniform or standard size during the clamping by the headers. The header assemblies are arranged so that separators may be selectively positioned therein. Such separators permit a given header assembly to be used in single pass, multiple pass, and compound heat exchanger installations. When tubes having deep grooves are provided, i.e., tubes having an outside diameter to groove depth of about four to one or less, the cooler may be mounted in a location where forced flow thereover can be provided solely by the slip stream of the propulsion screw.

United States Patent [72] Inventors [2!] Appl. No. [22] Filed (45]Patented [54] MARINE KEEL COOLER 21 Claims, 13 Drawing Figs.

[52] US. Cl 165/76, l15/0.5;28 5/l5,8: 165/44 [5 1] Int. Cl F28b 7/00[50] Field ofSearch 115/5;

il'i 's 8/1959 Pickford James Glenn Satterthwaite l Dogwood Trail,Portsmouth, Va. 23703;

James B. Macy, Jr., 107 Holly Lane,

Morehead City, N.C. 28557 $68,969

Oct. 8, 1969 Feb. 9, 1971 Continuation-impart of application Ser. No.

71 1, 646, Mar. 8, 1968, now abandoned.

Howe

Primary Examiner-Martin P. Schwadron Assistant Examiner-Theophil W.Streule AttorneyMcNenny, Farrington, Pearne and Gordon ABSTRACT: Amarine keel cooler is disclosed which includes two header assemblieseach adapted to be mounted on the exterior of a vessels hull. Eachheader assembly includes a stud plate and at least two separable membersformed of an elastomeric material. The members are formed withsemicylindrical recesses which cooperate with adjacent recesses to formopenings which receive and grip the ends of the heat exchanger tubes.Relatively soft heat resistant seals are positioned over the ends of thetubes within the openings and are tightly gripped when the parts of theheader assembly are bolted together. When fluted tubes are used, theparts are proportioned so that the tube is radially contracted to auniform or standard size during the clamping by the headers. The headerassemblies are arranged so that separators may be selectively positionedtherein. Such separators permit a given header assembly to be used insingle pass, multiple pass, and compound heat exchanger installations.When tubes having deep grooves are provided, i.e., tubes having anoutside diameter to groove depth of about four to one or less, thecooler may be mounted in a location where forced flow thereover can beprovided solely by the slip stream of the propulsion screw.

PATENTEHFEB 9:971 3,561,524

saw 1 [1F 3 PATENTED, FEB 9197:

SHEET 3 OF 3 MARINE KEEL COOLER This application is acontinuationin-part of our copending application, Ser. No. 711,646,filed Mar. 8, i968 now abandoned.

BACKGROUND OF THE lNVENTlON This invention relates generally to heatexchangers and more particularly to a novel and improved heat exchangerstructure particularly suited for use as a marine keel cooler.

PRIOR ART Various types of keel coolers are used to dissipate heat intothe water surrounding a vessel. Generally, such keel coolers include apair of headers externally mounted on the hull and connected to theinternal system by a through hull connection." Various types of tubesare connected between the headers to provide the principal heatexchanger surface. Usually the coolant for the equipment being cooled,such as the ship's engine or accessory equipment, is pumped through theheader and tubes where it is cooled before it is recirculated back tothe equipment being cooled. Examples of such keel cooler-type heatexchangers are illustrated in the U.S. Pat. Nos. 2,258,526 and3,177,936.

Although such keel coolers usually function properly, they presentseveral problems. For example, such prior keel coolers generally requirea through hull connection (a pipe or tube extending through the hull) toconnect the header to the internal system. Such through hull'connections provide a possible hull leak, particularly when the heatexchanger is damaged.

Prior keel coolers also involve considerable expense during installationand during repair. For example, it is usually necessary to separatelyassemble the tubes and headers and then assemble the entire keel coolerunit on the ships hull. Repair, for example, to replace a tube,therefore, generally requires the removal of the entire unit from thehull.

Further, when tubes of irregular shape are used because of their higherheat transfer capacity (such as the tube illustrated in the US. Pat. No.3,177,936), special fittings are usually required to mount the tubes onthe headers. This prevents stocking of bulk tubing in the field andincreases cost, since all tubes must first be cut to length and equippedwith special end fittings at the factory, prior to shipment andinstallation.

The depths of the grooves formed in the tubes of the type illustrated inthe US. Pat. No. 3,177,936 has also in the past been limited. Suchlimitation of groove depth occurs for two reasons. First, the use of anend fitting of the type illustrated in this patent blanks off the grooveareas and restricts flow into and out of the tube and tends to produce acondition in which the fluid flow is accelerated through the center ofthe tube and not through the fluted, or grooved portions. Secondly, deepnarrow grooves tend to produce an insulating, or dead" water layeraround the exterior of the tube which retards heat transfereffectiveness. Consequently, in the past, convoluted tubes of the typeillustrated in this patent have been limited to ratios of outsidediameter to groove depth of about 8 to l. Coolers using convoluted tubeswith outside diameter to groove depth ratios of about 8 to l andgreater, must have substantial length to provide the required coolingcapacity and subsequently, must be located on the vessels hull remotefrom the main propulsion screw where long flat surfaces are available inorder that the tubes may remain straight. In all such installations,positive movement between the vessels hull and the surrounding water isrequired before flow over the exterior of the tube occurs.

Still further, in most prior keel coolers, it has been impossible toincrease the heat exchange capacity or arrangement after the unit isinstalled on a vessel, without requiring extensive alterations.

SUMMARY OF INVENTION The present invention has several aspects. Inaccordance with one aspect of this invention a heat exchanger isprovided in which a simple low-cost structure effectively eliminates orminimizes most of the aforesaid problems and difficulties. The heatexchanger utilizes headers consisting of individual sections whichseparate along the 'centerline of the heat exchanger tubes. Preferably,the header parts are molded of an elastomeric or rubberlike materialwhich, when the header parts are clampedtogether, provides a sealedjoint between the header parts themselves and between the header partsand the tubes. The elastomeric headers may be reinforced with steel orother metal strengthening members around which the rubber is molded.

The headers are removably mounted on stud plates welded to the shipshull. These plates and the hull itself cooperate with the header partsto define the header chamber. It is, therefore, not necessary to utilizea through hull connection between the header and the internal system.

In accordance with another aspect; of this invention, convoluted tubeshaving axially extending grooves of the general type illustrated in theU.S. Pat. No. 3,177,936 extend between spaced headers to provide theheat exchanger surface. A molded elastomeric seal is positioned over theend of the tube so that the clamping of the header parts provides afluid-tight sealing connection and mechanical mounting for the tubes.Therefore, separately assembled end ttittings are not required thuspermitting the tubes to be cut to length on site and easily installed inthe headers while the headers are loosely mounted in place on the shipshull.

Because the clamping and sealing of the tube occurs along the externalsurface, the flow of the fluid enters directly into the grooved portionswithout restriction to provide better heat transfer. Consequently, thedepth of the grooves can be greatly increased with proportionateincreases in heat exchange efficiency and capacity with respect tosurface exposure and the fluid flow through the tubes. The occurrence ofinsulating dead water in the external grooves is prevented by forcingthe fluid coolant over the external surfaces of the tube. In accordancewith one embodiment in which the heat exchanger is used as a marine skincooler, the heat exchanger is located immediately adjacent to the ship'spropeller and directly in its slip stream. Consequently, cooling wateris forced over the exchanger tubes at any time the propulsion system isdelivering power, even though the ship may not be moving through thewater. Because of the greatly increased and high efficiency of heattransfer of a deep grooved tube in accordance with this invention, thelength of tubing required for a given amount of heat exchange capacityis greatly reduced when compared to conventional structures. This makesit possible to locate the heat exchanger along the curved and angledsurfaces of the hull directly in the slipstream of the main propulsionscrews, where forced flow occurs whenever heat dissipation is required.

Because the heat exchanger can be assembled in place on the hull, thecost of installation and handling is greatly reduced and it is a simplematter to remove and replace individual tubes when maintenance isrequired. In fact, the disassembly and reassembly of the heat exchangeris sufficiently simple to permit economical disassembly of the heatexchanger tubes to provide access to the hull for cleaning or paintingof the hull surface itself.

The illustrated heat exchanger incorporating this invention is alsoarranged so that the heat exchanger capacity can be increased by addingadditional tubes even after the heat exchanger is installed on thevessel. This is important in many installations since there is atendency to install larger engines during the life of a given vessel andsuch larger engines usually require greater heat exchanger capacity.Still further, it is possible with a heat exchanger incorporating thisinvention to rearrange the heat exchanger, even after installation, sothat a single heat exchanger assembly can be divided into separate heatexchanger subassemblies to provide cooling for additional equipmentinstalled on the vessel after the vessel is built and in service. Stillfurther, when the headers are formed of elastomeric material, theproblem of electrolytic corrosion is eliminated since the metal tubes ofthe heat exchanger are electrically insulated from the hull and from theinternal system connected to the heat exchanger.

OBJ ECTS OF INVENTION It is an important object of this invention toprovide a novel and improved heat exchanger particularly suited for useas a marine keel cooler.

It is another important object of this invention to provide a novel andimproved heat exchanger according to the preceding object which includesheaders formed of elastomeric material or the like.

It is another important object of this invention to provide a novel andimproved heat exchanger according to either of the preceding objectswherein through hull connections are not required between the headersand the connected internal system.

It is still another object of this invention to provide a heat exchangeraccording to any of the preceding objects wherein the headers are formedof parts which are separable along the centerline of the heat exchangertubes to facilitate installation and removal of such tubes.

It is still another object of this invention to provide a novel andimproved heat exchanger according to the last preceding object whereinclamping of the header parts automatically grips the heat exchangertubes and also provides a fluid seal between the tubes and the headers.

It is still another object of this invention to provide a novel andimproved heat exchanger according to the last preceding object whereintubes of irregular cross section are provided with formed gaskets at theheader to grip and seal the ends of the tubes.

It is still another object of this-invention to provide a novel andimproved heat exchanger according to the last preceding object whereintubes are formed with deep grooves to substantially increase the heatexchange area and efficiency and wherein means are provided to insureproper flow along both the inner and outer surfaces of the grooves.

Further objects and advantages will appear from the followingdescription and drawings wherein:

FIG. 1 is a side elevation of a heat exchanger incorporating thisinvention mounted on the exterior side of a hull of a vessel;

FIG 2 is an enlarged perspective view illustrating the structure of oneof the headers illustrated in FIG. 1 with three tubes in position andfurther illustrating a separator which may be used to divide the header;

FIG. 3 is an enlarged fragmentary section through one pair of tubesillustrating the mounting thereof;

FIG. 4 is a fragmentary perspective view illustrating the structure ofthe middle element of the heat exchanger;

FIGS. 5 and 6 are side and end views, respectively, of a fluted tubeillustrating a formed gasket mounted thereon;

FIGS. 7 and 8 are side end views of the end of a circular cross sectiontube with a gasket mounted thereon;

FIG. 9 is a perspective view of a stud plate adapted to use with aseparator installed in the header;

FIG. 10 is a view similar to FIG. 9 illustrating a stud plate of thetype used when a separator is not provided to divide the header;

FIG. 11 is a fragmentary view illustrating a heat exchanger inaccordance with this invention mounted adjacent to the main propulsionscrew of a ship where forced flow over the heat exchanger is provided bythe screw;

term keel cooler is broadly used herein and is intended to include heatexchangers mounted on a hull in anyundcr watcr location and is notlimited to heat exchangers mounted adjacent to the keel itself. The keelcooler includes two header assemblies 11 and 12 located at spaced pointson the hull 10. A plurality of heat exchanger tubes 13 extends betweenthe two headers 11 and 12 so that fluid entering the header assembly 11can pass through the tubes 13 to the header assembly l2 and be cooled bythe surrounding water. The tubes 13 illustrated in FIGS. 1 through 3, 5,and 6 are fluted tubes of the type disclosed in the US. Pat. No.3,l77.936. These tubes are formed with axially extending convolutions orfluting and the tube is symmetrical about its central axis 14 as bestillustrated in FIG. 6.

Welded to the interior of the .hull 10 adjacent to the header assembly11 is a threaded nipple l6 which communicates through an opening 17 inthe hull 10 to the chamber defined by the header assembly 11. Similarly,a second nipple I8 is welded to the hull 10 adjacent to the headerassembly 12 and communicates with the header chamber through an opening19 formed in the hull 10. Usually a valve body 21 is threaded into eachof the nipples l6 and 18 to close off the nipples when desired. Such avalve may be closed to prevent leakage of the surrounding water into thevessel in the event the keel cooler is damaged.

In the typical installation the cooling water from the vessel's powerplant is-pumped through the nipple 16, the header assembly 11, alongwith tubes 13, and through the header assembly 12 for recirculation backto the power .plant through the nipple 18. It should be understood,however,.that the keel cooler incorporating this invention may be usedto .provide cooling of any type of equipment within the vessel whichrequires the rejection or absorption of heat energy.

Referring now to FIGS. 2 and 3 each of the header assemblies 11 and 12embody a similar structure so a detailed description of the structure ofthe header assembly 12 should be understood to be equally applicable tothe structure of the header assembly 11. The header assembly 12 includesa stud plate 22 which is rectangular in shape and which is welded at 23to the hull 10; The shape of the stud plate 22 is best illus trated inFIG. 10. The weld 23 extends along the entire periphery of the studplate 22 and provides a fluid-tight joint therebetween.

Spaced around the stud plate 22 are a plurality of tapped holes 24 eachof which is adapted to receive a clamp bolt 26. The bolts 26 extendthrough an outer cover member 27, an intermediate member 28 and an innermember29, and operate to clamp each of the members 27 through 29 againstthe stud plate 22. The bolts 26 are preferably socket head-type boltsand the outer member 27 is preferably recessed so that the heads of thebolts are flush with the end surface of the header.

The three members 27, 28, and 29 are preferably molded of an elastomericmaterial with the outer member 27 formed of a relatively hard materialhaving a durometer in the order of 90 D and the inner members 28 and 29formed of material having a durometer in the order of C. With such anarrangement the outer member is quite rigid and is substantiallydimensionally stable so that the clamping forces-of the bolts-26 aresubstantially uniformly distributed along the joint between it and theintermediate member 28. With such a substantially rigid outer member 27it is not necessary to provide an excessive number of clamping bolts inorder to provide the uniform clamping force. The inner members 28 and 29being somewhat softer, can deform to a sufficient degree so that a sealis provided between its outer surface and the inner surface of the outermember 27. Similarly a fluid-tight joint is provided between theinterengaging surfaces 33 and '34 of the two members 28 and 29,respectively. This slight deformation of the inner member 29 alsoassures a fluid-tight joint between its inner surface 36 and the outersurface 37 of the stud plate 22.

The outer member 27 is formed with an end wall 38 extending thercacrosswhich cooperates with the rectangular-members 28 and 29, and with thestud plate 22 and hull to define a header chamber 39 which is generallyrectangular in shape as best illustrated in H6. 2. Proper positioning ofthe inner member 29 in respect to the stud plate 22 is assured bylocating projections 41 which fit into locating recesses 42 formed inthe stud plate 22. Proper alignment between the members 27 through 29does not require such locating projections and recesses since the bolts26 can easily be inserted in their aligned openings.

The inner member 29 is formed with a plurality of semicylindrical tubegripping recesses 43 along one side 44. In the embodiment illustrated inFIG. 2 there are eight similar recesses 43 formed in the inner member29. The intermediate member 28 is formed with eight similarsemicylindrical tube gripping recesses 46 which are located in registrywith the recesses 43 and cooperate therewith, when the members 28 and 29are clamped together, to form eight cylindrical openings each adapted toreceive the end of a tube 13. A second group of eight similarsemicylindrical recesses 47 and 48 are formed in the two members 28 and27, respectively, which cooperate to form a second group of cylindricalopenings when these two members are clamped together. Each of theseopenings is also adapted to receive and grip the end of a tube 13.Therefore, in the illustrated structure, there are 16 heat exchangertubes 13 arranged in two groups of eight.

Each of the heat exchanger tubes is provided with a relatively soft heatresistant elastomeric seal gasket 51 positioned over its end asillustrated in FIGS. 5 and 6. The outer surface 52 of the seal 51 iscylindrical and the inner surface thereof 53 is shaped to conform to theouter surface 54 of the tube 13. The seal may be molded separately andslipped over the end of the tube 13 or may be formed with an axial cut56 to facilitate the position of the seal around the tube. The variouselements are proportioned so that the outer surface 52 is cylindricaland has a diameter slightly larger than the diameter of the openingsformed by the recesses 43, 46, 47, and 48. Consequently, clamping of themembers 27, 28, and 29, after the ends of the tubes are positioned inthe recesses, causes releasable compressive stress to be uniformlyapplied to the seals 51 to form a fluid-tight joint between the tubes 13and the associated members of the header assembly.

Because the elastomeric gasket 51 grips and seals with the exteriorsurface of the tube, there is no restriction resisting passage of thefluid into and out of the tube from the header. In the past, when usingfluted tubing, it has been customary to provide an adapter of the typeillustrated in the US. Pat. No. 3,177,936. Such an adapter provides anentrance passage of circular section having a diameter less than the ID.of the fluted tube while completely blanking off the fluted passages.Consequently, such adapters reduce the area at the inlet and outlet ofthe tube and seriously restrict both the flow and access of the fluid tothe extended fluted surfaces. Further, these adapters tend to produceaccelerated flow along the center of the tube so that the fluid passesthrough the tube without making good heat exchange contact with thefluted surface. In fact, in this patent a spiral baffling arrangement isprovided to deflect the flow through the tube outward into the groovedareas for greater heat exchange efficiency even though the grooves arevery shallow.

In the structure of the present invention, however, the fullcross-sectional area within the tube is directly open to the headers sono restriction is provided to resist flow in and out of the tubeFurther, since the fluid entering the tube flows directly into thegrooved portions, the flow occurs along the extended surfaces of thetube and greater heat exchange efficiency is achieved.

It should be noted that fluted tubing of the type illustrated isdifficult to manufacture to extremely close tolerances and that the sizeof the tubing when unstressed varies a substantial amount. it is,therefore, preferable to size the various elements so that the clampingof the members around the ends of the tube cause the tube to be radiallycontracted to a size slightly smaller than the smallest tube sizenormally manufactured. With this arrangement tight gripping is providedfor all the various sizes encountered within the normal tolerances ofmanufacture of a given tubing size.

' Referring to H05. 7 and 8, standard cylindrical tubing 58 may also bemounted in the headers where the greater heat exchange surface of afluted tube is not required. in this embodiment a seal 59 is againpositioned over the end ofthe tube before it is clamped in position inthe header assembly. Since circular tubing is manufactured to relativelyclose tolerances, sufficient elasticity is provided in the seal 59 toinsure proper sealing and mounting of tubes in the header assemblieswithout appreciable deformation of the tube itself. The various elementsare again proportioned so that the outer surface 61 of the seal 59 isslightly larger than the opening provided by the associated recesses sothat the seal is subjected to releasable compressive stress to insureproper gripping and sealing.

it should be noted that the recesses 48 in the end member 27 arepositioned in alignment with the recesses 43 in the inner member 29.Therefore, the outer member 27 can be as sembled against the innermember 29 without the intermediate member 28 when a heat exchangerhaving only eight tubes is required. Similarly additional intermediatemembers 28 can be inserted when more than two groups of tubes arerequired to provide sufficient heat exchange capacity. Therefore, with astructure in accordance with this invention a heat exchanger havingeight tubes, for example, may be installed on a vessel when the vesselis constructed, and by adding additional intermediate members the heatexchanger capacity can be easily changed without large labor or materialexpense.

Although only three tubes are illustrated in H6. 2, to simplify theunderstanding of this invention, it should be understood that normallyl6 tubes would be mounted in such a header assembly. However, if only 13tubes were required, for example, suitable plugs are inserted in theother three openings. Preferably such plugs include a solid piece ofcylindrical metal provided with a seal similar to the seal 59.

Because special fittings are not required on the ends of the tubes 13,they may be cut to length on site and it is a simple matter to positiona seal therearound and install such tubes and a header. This providesflexibility and materially decreases the labor and expense involved inthe installation of the heat exchanger. Further, in the event that oneof the tubes must be replaced, because of damage or the like, it is asimple matter to loosen the screws 26 to release: the clampingengagement with the seals 51 and thereafter removal is achieved by axialmovement of the tube to free first one end and then the other end.Reinsertion of the replacement tube may be accomplished in the oppositemanner. For this reason it is preferable to arrange the seals so thatthe outer surfaces 52 have a diameter at least as great or greater thanthe largest diameter of the adjacent portion of the tube.

In the heat exchanger illustrated in FIG. 1 a single pass is providedwith the fluid to be cooled flowing into the header assembly 11 and outof the header assembly 12. In some installations, however, it may bedesirable to provide two or more passes. In such installations aseparator 66 is used. The separator is preferably formed of a relativelyhard elastomeric material which is provided with projections 67 and 68adapted to fit into a pair of vertically extending grooves 69 formed inthe members 27 through 29. The separator 66 is preferably formed with avertical height, when unstressed, which is slightly greater than thevertical height of the header chamber 39. It is also preferably sized toslide with a relatively snug fit into the grooves 69. When a separatoris used, the stud plate is provided with a center wall 71 positioned toengage the top surface of the separator. The stud plate 70 illustratedin FIG. 9 is provided with a center wall substantially midway betweenits ends and is used when a separator 66 is inserted in the centralnotches 69. As the bolts 26 are tightened, the separator 66 en gages thesurface of the center wall 71 on one side and the end wall 38 on theother side and is deformed from an unstressed condition. This causes theseparator to deform laterally forming a tight seal between the separatorand the inner surfaces of the members 27 through 29.

In a two pass heat exchanger a single separator 66 is normally mountedin the center of one header assembly to divide it into two similarchambers, each connected through an opening 19a and 19b to the connectedinternal system. The other header is not provided with a separator insuch an installation so that cooling fluid passes through one group oftubes in one direction and back to the divided header through the othertubes. ln such an installation the undivided header assembly is notprovided with internal connections.

A compound heat exchanger can be provided by using separators in eachheader to completely separate one group of tubes from the other group oftubes. In such an installation a connection is provided between eachseparate header chamber and the associated system. A single heatexchanger assembly can then be used to cool two separate systems. Itshould also be noted that a groove 69 is provided between each group oftube gripping surfaces so that the separator can be selectivelypositioned to separate any desired number of tubes from the other tubes.Of course the stud plate should be provided with an appropriatelylocated cross wall 71 for the paiticular installation.

With a heat exchanger incorporating this invention, considerable savingsin cost of manufacture, installation, and maintenance are provided. Bythe proper use of intermediate members and separators, it is possible touse standard header assembly parts for a large variety of heat exchangerarrangements.

The headers illustrated in the drawings have tube gripping openings onlyon one side. However, it should be understood that headers may be formedwith tube gripping openings on one or more sides so that tubes canextend from the header in more than one direction. For example, a headerwith tube gripping openings on opposite sides may be mounted between twoheaders of the type illustrated in FIG. 2. Separate tubes are thenmounted to extend between the center header and each of the two endheaders. With this arrangement a relatively long heat exchanger can beprovided without requiring the use of excessively long tubes.

Since the tubes are mounted in elastomeric material which iselectrically insulating in character, electrolytic corrosion is notencountered and it is not necessary to provide separate structure toprevent such corrosion. Still, further, the use of a stud plate weldeddirectly to the hull, to mount the header assemblies, eliminates theneed of through hull connections. Therefore, in the event that the heatexchanger is damaged during use, there is no tendency to damage theconnecting piping within the hull. In fact, the bull in the area of theheat exchanger is reinforced by the stud plates so the likelihood ofleakage damage is extremely remote. Since the tubes can be removed orreplaced with ease and since the header assemblies are formed of anoncorrosive material, it is practical to disassemble the heat exchangerfor such purposes as providing access to the portion of the hullunderneath the tubes when the hull needs scraping and painting.

FlGS. l 1 through 13 illustrate a further aspect of this invention. Inthe embodiments of FIGS. Ill through 13 the tube is formed with deepgrooves and consequently, the tubes provide far greater heat exchangesurface area for a given tube diameter. in the past, fluted tubes havebeen formed with a ratio of outside diameter to groove depth in theorder of 8 to 1. For example, a tube having lrinch outside diameternormally has been formed with a grooved depth in the order ofthree-sixteenths of an inch. Such a tube is substantially as illustratedin FIG. 6. However, in accordance with this invention, tubes can beformed with outside diameter to groove depth ratios as low as three toone, as illustrated in FIG. 12, and lower, depending only uponmanufacturing limitations. in this tube the groove depth is one-halfinch and the outside diameter of the tube is lrlllChES. This can usuallybe accomplished without decreasing the number of flutes in the tube andthe resulting tube has about 300 percent greater surface area for agiven outside diameter than the prior art tubes. 1

The tube 91 illustrated in FIG. 12 is provided with a seal 92 I formedof a relatively soft heat resistant elastomeric material so that it canbe mounted in the header 12. Here again, the seal is proportioned sothat it has a cylindrical outer surface and is shaped to conform to thetube surface along its inner surface. Also, the seal is sized so that itis gripped tightly in the header and is releasably compressed to asufficient degree to provide a positive seal with the tube and apositive mounting for the tube. Because the seal 92 engages the outersurface of the tube, the ends of the flutes 93 are open to the headerand flow is not restricted into and out of the flutes or the centerportion 94.

Because of the substantial depth of the grooves in the tube 91, heatexchangers employing such tubes, when immersed in liquid, should bearranged so that there is a forced flow offluid over the outside of thetube in order to prevent insulating deadwater in the grooves. Therefore,when a tube of this type is utilized as a skin or keel cooler on a ship,it is desirable to mount the heat exchanger so that flow over the heatexchanger is insured under all conditions of operation. It is thereforepreferable to mount the heat exchanger in the slipstream of the mainpropulsion screw of the ship. When located in such a position, flow ofcooling water over the heat exchanger tubes is insured whenever thepropulsion system of the ship is developing power and requiressubstantial heat dissipation. Because the tubes have a very high'heatexchange efficiency, that is, are capable of dissipating'substantialamounts of heat for a given length of tubing, the length of such heatexchanger tubes required for a given engine is greatly reduced and it ispractical to mount the heat exchanger even along the curved and angledsurfaces of the hull adjacent to the propeller.

FIG. 11 illustrates such a mounting wherein a heat exchanger 96,provided with tubes 91 extending between the headers 11 and 12, ismounted adjacent to the main propulsion screw 97 of a ship and along acurved portion 98 of the ships hull. Fairing blocks 101 may be mountedadjacent to the header 12. In this location flow of cooling water overthe heat exchanger tubes 91 is assured whenever the screw 97 is turningand adequate heat exchanger efficiency is therefore provided wheneverheat dissipation is required. ln the past, because of the greater lengthof tubing required, it has been customary to mount the heat exchangersalong the flat bottom portion of the hull forward of the location 99.However, in such installations, deep grooved tubes could not be used inmany cases since forced flow of the water over the tubes was createdonly by movement of the hull through the water. In many marineinstallations substantial amounts of power may be delivered withoutappreciable hull movement. in operations of tow boats, tugs or the like,substantial amounts of power must often be delivered for extendedperiods of time even though the boat is not moving to any appreciableextent. Such a situation can occur when a tow boat is startinga longtow, or when a part of the tow is grounded on a bar in the river andprolonged maneuvering is required at full power without appreciablerelative movement between the hull and the surrounding water.

It should be understood, because of its high capacity and very shortlength, the heat exchanger can be located in areas normally prohibitiveto other type coolers. For example, it may, in some instances, belocated stemward of the screw 97:

FIG. 13 illustrates another deep grooved tube 102. This tube 102 isprovided with the same number of flutes as the tube illustrated in FlG.12, but is provided with a groove threeeighths inch deep. Such a tubedoes not provide as much heat exchange surface for a given outsidediameter, but does provide about 200 percent greater surface area thanthe shallow fluted tube of the type illustrated .in H0. 6. Here again,the tube is mounted in a seal 103 which engages its outer surface anddoes not restrict flow into the flutes of the tube. Such a tube shouldalso be used in an installation wherein sufficient flow is presentalongthe exterior surface of the tubes to prevent the build up ofadeadwater insulation zone inthecxterior grooves of the tube.

in the tubes illustrated in FIG. 12, the ratio of tube outside diameterto groove depth is about 3 to 1. In the tube of FIG. 13, the ratio oftube outside diameter to groove depth is about 4 to 1. In both cases,the ratios are substantially less than the ratio of 8 to l heretoforeconsidered to be the minimum usable ratio of outside diameter to groovedepth for this type of tubing.

Although preferred embodiments of this invention are illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the inventiondescribed and claimed herein.

We claim:

1. A heat exchanger comprising at least a pair of spaced headers, and aplurality of heat exchanger tubes extending between said headers, saidheaders each including first and second separable members, said memberseach being formed with tube gripping surfaces along the jointtherebetween which cooperate with associated tube gripping surfaces onthe other member to encircle the end of a tube, nd clamp meansreleasably operable to clamp said members together to form a fluid-tightjoint between said members and to cause said tube gripping surfaces togrip the ends of said tubes forming a fluid seal therewith, said memberscooperating to define at least part of a header chamber open to saidtubes, release of said clamp means permitting relative axial movementbetween individual tubes and header for removal and replacement ofindividual tubes without moving said headers toward or away from eachother.

2. A heat exchanger as set forth in claim 1 wherein said headers areadapted to be mounted on the exterior of the hull of a vessel, saidheaders having openings proportioned to fit against the exterior of thehull and be closed thereby, said members when mounted on said hullcooperating with a portion of said hull to define a header chamber.

3. A heat exchanger as set forth in claim 1 wherein said associatedgripping surfaces are semicylindrical and cooperate to form cylindricalgripping openings when said members are clamped together.

4. A heat exchanger as set forth in claim 3 wherein a resilient sea! ispositioned on the ends of said tubes within said gripping openings,saidclarnp means causing said seals to be subjected to compressivestress to provide gripping and sealing between said tubes and header,release of said clamping means releasing said seals and permitting axialmovement between said headers and tubes.

5. A heat exchanger as set forth in claim 4 wherein said tube isnoncircular and the inner surface of said seal conforms to the exteriorsurface of said tube.

6. A heat exchanger as set forth in claim 5 wherein said tube is axiallyfluted and is substantially symmetrical with respect to its centralaxis, and the wall of said tube is radially contracted from itsunstressed condition substantially to a standard size when said seal isclamped between said tube gripping surfaces.

7. A heat exchanger as set forth in claim 4 wherein the diameter of theexterior surface of said seal is greater than the maximum diameter ofsaid tube adjacent said end whereby release of said clamping meanspermits axial movement of said tube with respect to said header membersin both directions.

8. A keel cooler including a heat exchanger as set forth in claim 7wherein said seal is fonned of electrical insulating material and isadapted to electrically insulate said tube from the hull of a vessel.

9. A heat exchanger as set forth in claim 8 wherein a separator isadapted to be removably positioned in said header chamber to separatesaid chamber into at least two separate chambers, and each separatechamber is open to at least one pair of tube gripping surfaces.

10. A heat exchanger as set forth in claim 1 wherein said headers eachinclude a third separable member which cooperates with said secondmember to provide additional opposed pairs of tube gripping surfaces,said additional opposed pairs of tube gripping surfaces being spacedfrom the joint between said first and second members.

ild

11. A keel cooler comprising a header assembly defining at least part ofa header chamber, said assembly including a substantially rigid firstmember adapted to be mounted on the hull of a vessel, a substantiallyrigid second member and an intermediate member formed of material whichis softer than the material forming said first and second members, saidintermediate member and at least one of said first and second membersbeing formed with mutually engageable surfaces providing a fluid tightseal therebetwcen when clamped together and opposed tube grippingsurfaces, :1 tube, a resilient seal around the end of said tube adaptedto be positioned between said tube gripping surfaces, and releasableclamp means adapted to clamp said intermediate member between said firstand second members and tightly clamp said seal causing said seal toprovide a fluid-tight joint between said two members and said tube,release of said clamping means permitting axial movement of said tubewith respect to said members.

12. A keel cooler as set forth in claim 11 wherein said first member isa metal stud plate, and said second member and said intermediate membersare formed of elastomeric material, and said clamp means is a pluralityof threaded fasteners connected to said stud plate.

13. A keel cooler as set forth in claim ll wherein a second intermediatemember is provided between the first inter mediate memberand said firstmember, said first and second intermediate members being formed withmutually engagedble surfaces providing a fluid-tight seal therebctweenwhen clamped together and opposed tube gripping surfaces adapted to gripthe seal at an end of said tube.

14. A keel cooler comprising a hull of a vessel, a header assemblycooperating with the exterior surface of said bull to define a headerchamber, said hull being formed with an opening therethrough providingflow passage into said header chamber, conduit means secured to theinterior of said hull around said opening, said header assemblyincluding at least two separable members fonned with mutually engageablesurfaces providing a fluid-tight seal therebetwcen when clamped togetherand opposed tube gripping surfaces, a tubc, a resilient seal around theend of said tube adapted to be positioned between said tube grippingsurfaces, and releasable clamp means releasably clamping said memberstogether and tightly clamping said seal causing said seal to provide afluidtight joint between said members and said tube, release of saidclamping means permitting axial movement of said tube with respect tosaid two members.

15. In combination a hull of a vessel, a stud plate welded to theexterior surface of said hull, a conduit mounted on the inside of saidbull in alignment with said stud plate, a header assembly removablymounted on said: stud plate cooperating with said hull and plate todefine a header chamber, a plurality of heat exchanger tubes mounted onsaid header assembly, and an opening in said hull providing a'flowpassage between said conduit and chamber.

16. A combination as set forth in claim 15 wherein said header assemblyincludes at least two separable members formed of elastomeric material,one of said members being positioned between said stud plate and theother of said members, and said one member being formed of softerelastomeric material than the elastomeric material of said other member17. A heat exchanger comprising a pair of spaced headers, a tubeextending between said headers formed with axial fluting substantiallysymmetrical with respect to the central axis thereof, an elastomericseal at each end of said tube engaging the outer surface of saidfluting, said seal when unstressed being formed with an .inner surfacesubstantially conforming to the outer surface of the adjacent end ofsaid fluting, said headers being provided with means to releasably clampsaid seals into tight engagement with said outer surface of said tube tomount said tube on said headers and to provide a fluid seal between saidtube and the adjacent headers, said seals and said clamping meansproviding substantially no restriction of flow between said headers andsaid tubes.

semicylindrical clamping surfaces proportioned to engage and grip theassociated seals.

21. A heat exchanger as set forth in claim l9 wherein said heatexchanger is mounted on the hull of a ship having a propulsion screw andis located with respect to said screw so that operation of said screwforces sufficient coolant water over the exterior surfaces of said tubewithout movement of the ship through the water being required.

1. A heat exchanger comprising at least a pair of spaced headers, and aplurality of heat exchanger tubes extending between said headers, saidheaders each including first and second separable members, said memberseach being formed with tube gripping surfaces along the jointtherebetween which cooperate with associated tube gripping surfaces onthe other member to encircle the end of a tube, nd clamp meansreleasably operable to clamp said members together to form a fluid-tightjoint between said members and to cause said tube gripping surfaces togrip the ends of said tubes forming a fluid seal therewith, said memberscooperating to define at least part of a header chamber open to saidtubes, release of said clamp means permitting relative axial movementbetween individual tubes and header for removal and replacement ofindividual tubes without moving said headers toward or away from eachother.
 2. A heat exchanger as set forth in claim 1 wherein said headersare adapted to be mounted on the exterior of the hull of a vessel, saidheaders having openings proportioned to fit against the exterior of thehull and be closed thereby, said members when mounted on said hullcooperating with a portion of said hull to define a header chamber.
 3. Aheat exchanger as set forth in claim 1 wherein said associated grippingsurfaces are semicylindrical and cooperate to form cylindrical grippingopenings when said members are clamped together.
 4. A heat exchanger asset forth in claim 3 wherein a resilient seal is positioned on the endsof said tubes within said gripping openings, said clamp means causingsaid seals to be subjected to compressive stress to provide gripping andsealing between said tubes and header, release of said clamping meansreleasing said seals and permitting axial movement between said headersand tubes.
 5. A heat exchanger as set forth in claim 4 wherein said tubeis noncircular and the inner surface of said seal conforms to theexterior surface of said tube.
 6. A heat exchanger as set forth in claim5 wherein said tube is axially fluted and is substantially symmetricalwith respect to its central axis, and the wall of said tube is radiallycontracted from its unstressed condition substantially to a standardsize when said seal is clamped between said tube gripping surfaces.
 7. Aheat exchanger as set forth in claim 4 wherein the diameter of theexterior surface of said seal is greater than the maximum diameter ofsaid tube adjacent said end whereby release of said clamping meanspermits axial movement of said tube with respect to said header membersin both directions.
 8. A keel cooler including a heat exchanger as setforth in claim 7 wherein said seal is formed of electrical insulatingmaterial and is adapted to electrically insulate said tube from the hullof a vessel.
 9. A heat exchanger as set forth in claim 8 wherein aseparator is adapted to be removably positioned in said header chamberto separate said chamber into at least two separate chambers, and eachseparate chamber is open to at least one pair of tube gripping surfaces.10. A heat exchanger as set forth in claim 1 wherein said headers eachinclude a third separable member which cooperates with said secondmember to provide additional opposed pairs of tube gripping surfaces,said additional opposed pairs of tube gripping surfaces being spacedfrom the joint between said first and second members.
 11. A keel coolercomprising a header assembly defining at least part of a header chamber,saId assembly including a substantially rigid first member adapted to bemounted on the hull of a vessel, a substantially rigid second member andan intermediate member formed of material which is softer than thematerial forming said first and second members, said intermediate memberand at least one of said first and second members being formed withmutually engageable surfaces providing a fluid tight seal therebetweenwhen clamped together and opposed tube gripping surfaces, a tube, aresilient seal around the end of said tube adapted to be positionedbetween said tube gripping surfaces, and releasable clamp means adaptedto clamp said intermediate member between said first and second membersand tightly clamp said seal causing said seal to provide a fluid-tightjoint between said two members and said tube, release of said clampingmeans permitting axial movement of said tube with respect to saidmembers.
 12. A keel cooler as set forth in claim 11 wherein said firstmember is a metal stud plate, and said second member and saidintermediate members are formed of elastomeric material, and said clampmeans is a plurality of threaded fasteners connected to said stud plate.13. A keel cooler as set forth in claim 11 wherein a second intermediatemember is provided between the first intermediate member and said firstmember, said first and second intermediate members being formed withmutually engageable surfaces providing a fluid-tight seal therebetweenwhen clamped together and opposed tube gripping surfaces adapted to gripthe seal at an end of said tube.
 14. A keel cooler comprising a hull ofa vessel, a header assembly cooperating with the exterior surface ofsaid hull to define a header chamber, said hull being formed with anopening therethrough providing flow passage into said header chamber,conduit means secured to the interior of said hull around said opening,said header assembly including at least two separable members formedwith mutually engageable surfaces providing a fluid-tight sealtherebetween when clamped together and opposed tube gripping surfaces, atube, a resilient seal around the end of said tube adapted to bepositioned between said tube gripping surfaces, and releasable clampmeans releasably clamping said members together and tightly clampingsaid seal causing said seal to provide a fluid-tight joint between saidmembers and said tube, release of said clamping means permitting axialmovement of said tube with respect to said two members.
 15. Incombination a hull of a vessel, a stud plate welded to the exteriorsurface of said hull, a conduit mounted on the inside of said hull inalignment with said stud plate, a header assembly removably mounted onsaid stud plate cooperating with said hull and plate to define a headerchamber, a plurality of heat exchanger tubes mounted on said headerassembly, and an opening in said hull providing a flow passage betweensaid conduit and chamber.
 16. A combination as set forth in claim 15wherein said header assembly includes at least two separable membersformed of elastomeric material, one of said members being positionedbetween said stud plate and the other of said members, and said onemember being formed of softer elastomeric material than the elastomericmaterial of said other member.
 17. A heat exchanger comprising a pair ofspaced headers, a tube extending between said headers formed with axialfluting substantially symmetrical with respect to the central axisthereof, an elastomeric seal at each end of said tube engaging the outersurface of said fluting, said seal when unstressed being formed with aninner surface substantially conforming to the outer surface of theadjacent end of said fluting, said headers being provided with means toreleasably clamp said seals into tight engagement with said outersurface of said tube to mount said tube on said headers and to provide afluid seal between said tube and the adjacent headers, said seals andsaid clamping means providing substantiAlly no restriction of flowbetween said headers and said tubes.
 18. A heat exchanger as set forthin claim 17 wherein means are provided to force fluid to flow over theexterior surfaces of said tube.
 19. A heat exchanger as set forth inclaim 18 wherein the ratio of the outside diameter of said tube to thedepth of the grooves formed by said fluting is at least as small asabout 4 to
 1. 20. A heat exchanger as set forth in claim 19 wherein saidseals are provided with cylindrical outer surfaces, and said headers areformed of separable members providing semicylindrical clamping surfacesproportioned to engage and grip the associated seals.
 21. A heatexchanger as set forth in claim 19 wherein said heat exchanger ismounted on the hull of a ship having a propulsion screw and is locatedwith respect to said screw so that operation of said screw forcessufficient coolant water over the exterior surfaces of said tube withoutmovement of the ship through the water being required.